Vacuum cleaners which utilise cyclonic separating apparatus are well known. Examples of such vacuum cleaners are shown in EP 0 042 723, EP 1 370 173 and EP 1 268 076. In general, an airflow in which dirt and dust is entrained enters a first cyclonic separator via a tangential inlet which causes the airflow to follow a spiral or helical path within the first cyclonic separator so that the dirt and dust is separated from the airflow. Relatively clean air passes out of the chamber while the separated dirt and dust is collected in a first collector. In some applications, and as described in EP 0 042 723, the airflow is then passed to a second cyclonic separator which is capable of separating finer dirt and dust than the first cyclonic separator. The cleaned airflow then exits the cyclonic separating apparatus, and the separated fine dirt and dust is collected in a second collector.
The absence of a bag in a cyclonic vacuum cleaner can create difficulties for the disposal of the dirt and dust which is collected by the cleaner. When the collectors of a vacuum cleaner such as that described in EP 0 042 723 become full, a user typically removes the cyclonic separating apparatus from the main body of the machine and tips the collectors upside down. Often it may be necessary for the user to dislodge the dirt manually, which can be inconvenient.
An improved arrangement is disclosed in EP 1 023 864, which describes a vacuum cleaner with separating apparatus which can be removed from a main body of the cleaner for emptying. A lower closure of the separating apparatus is attached by way of a hinge to the remainder of the separating apparatus and the closure can be released by pressing a release button. Although it is desirable to provide a separating apparatus which can be emptied in this way, it can be difficult to seal the lower closure reliably against the remainder of the separating apparatus.
An improved sealing arrangement is described in EP 1 370 172. The described vacuum cleaner has a first and a second cyclonic separator, each having a separate collector. The collectors are annular and the first collector surrounds the second collector. Attached to the lower end of an annular wall separating the two collectors is a depending annular seal. A hinged closure member is connected to the base of the first collector and which can be released to empty the two collectors. When the closure member is moved to a closed position, the seal is wiped against a part of the closure member, ensuring that the sealing surface is clear of dirt and dust, and allowing the seal to be stretched slightly by engagement with the closure member when in the closed position. This helps to maintain the sealing action.
An alternative sealing arrangement is used on a range of vacuum cleaners sold by Dyson™ under the trade name DC12™. These vacuum cleaner also have two cyclonic separators, each having a separate collector. In this arrangement, a hinged closure member carries a small annular seal which seals against a wall separating the two collectors.
However, a problem associated with both of the above arrangements is that the seal may become less effective with use; for example, the seal may become worn or brittle and may not seal correctly. Also, with an arrangement using a movable closure member, there is a risk that the user may not return the closure member to the correct closed position after emptying the collectors. The above situations may lead to ineffective sealing between the collectors and leaks occurring therebetween. This is undesirable because separated dirt and dust can move between the collectors and may become re-entrained in the airflow, reducing the efficiency at which the cyclonic separating apparatus operates. Leaks between collectors may also lead to unwanted pressure drops, again reducing the efficiency at which the cyclonic separating apparatus operates.
Some, more recent, vacuum cleaners include cyclonic separating apparatus which has more than two cyclonic separators or separation stages. Cyclonic separating apparatus including three cyclonic separators is disclosed in WO 2006/125944, in which, three collectors are required—one for each cyclonic separator. Clearly, the greater the number of collectors which are provided, the greater is the risk of leaks occurring between these collectors if they are not sealed correctly.